1. Field of the Invention
The present invention relates to a compressor for a fluid such as a refrigerant compressor used in a refrigeration cycle of an air-conditioning system mounted in a vehicle.
2. Description of the Related Art
There are two leading types of conventional drive plate (or swash plate) type piston compressors. One type takes out reciprocating motion directly to a piston by bringing two semispherical shoes attached to the end of the piston into direct frictional contact with the front and rear surfaces of a drive plate attached to a shaft in a tilted state and engaging in rotary motion and rocking motion. The problem with a compressor of this type is that at the time of high speed rotation of the compressor, the relative sliding speed between the drive plate and the shoes becomes large, so under operating conditions where the supply of lubrication oil becomes insufficient, the lubrication state between the drive plate and shoes becomes poor and seizing or other trouble easily occurs. Further, since the drive plate and the shoes engage in frictional contact, there is also the problem of a large mechanical loss compared with rolling contact.
The other type changes the large frictional sliding contact between the drive plate and shoes to rolling contact to reduce the mechanical loss etc. One example is described in Japanese Unexamined Patent Publication (Kokai) No. 2001-123945.
In this type, one end of each piston has attached to it shoes able to freely tilt with respect to an axis of the piston. Further, a thrust needle bearing is interposed between the shoes and the drive plate so that the sliding contact parts become rolling contact parts. These constituent elements enable a compression operation pushing the piston into the cylinder bore to compress the fluid, but do not enable a suction operation of pulling the piston out from the cylinder bore to suck the fluid. The reason is that the thrust needle bearing can support a compressive load in the axial direction, but cannot transmit or support a tensile load.
Therefore, the compressor described in the above-mentioned Japanese Unexamined Patent Publication (Kokai) No. 2001-123945 is configured to enable a suction operation by providing a rocking member engaging with and holding the shoes attached to the end of a piston with a suitable clearance and a slider slidably engaging with the shaft in the axial direction, by connecting the rocking member and slider by a roller bearing, and by biasing the slider toward the drive plate by a coil spring. The compressor of this example is a fixed capacity type, but even if making the tilt angle of the drive plate variable to try to remodel the compressor to a variable capacity type, with this configuration, it is impossible to change the tilt angle of the rocking member engaged with and holding the shoes, so this compressor cannot be made a variable capacity type.
Further, in this example, in the same way as the structure in general use in a conventional compressor of this type, the shaft passes through the center of the drive plate and the rocking member (shoe holding plate) driven by this through a bearing and extends to the inside of the cylinder block, so a bearing is provided inside the cylinder block to support the front end of the shaft. In this case, while there is nothing which has to be driven by the shaft other than the drive plate, since the shaft passes through the rocking member etc. and extends to the cylinder block at the rear, there is the problem that the compressor as a whole becomes larger than necessary.
Further examples of the conventional compressor are shown in Japanese Unexamined Patent Publication (Kokai) No. 7-19164 and Japanese Unexamined Patent Publication (Kokai) No. 2001-234857. One structure is illustrated in FIG. 38. These compressors fall under the category of drive plate type (or swash plate type) piston type variable capacity compressors. The housing forming the shell is comprised of three partsxe2x80x94front housing 1, a cylinder block 2, and a rear housing 3xe2x80x94joined by means such as not shown through bolts. Pistons 7 are inserted into the plurality of cylinder bores 21 formed in the center cylinder block 2 and are forced to engage in reciprocating motion by a common drive plate (swash plate) 5 through shoes 8. The drive plate 5 is driven to rotate by a long shaft 4 passing through its center and extending to the center of the cylinder block 2. The front end of the shaft 4 is axially supported by a bearing 64 provided in the cylinder block 2.
In the operating state, due to the rocking motion of the drive plate 5 rotating together with the shaft 4, the pistons 7 engage in reciprocating motion in their cylinder bores 21 to expand and compress working chambers 21a and thereby cause a fluid such as a refrigerant to pass through a suction valve 13 and be sucked into the working chambers 21a from a suction chamber 31 formed at the center of the rear housing 3 so as to be compressed, then pass through a discharge valve 11 and be discharged into a large volume discharge chamber 32 formed at the outer periphery of the rear housing 3. This compressor enables the tilt angle of the drive plate 5 to be smoothly changed, so enables the discharge capacity to be continuously changed.
In a compressor of the type causing pistons to engage in reciprocating motion to compress a fluid, both the suction operation from the suction chamber 31 to the working chambers 21a and the discharge operation of the fluid compressed in the working chambers 21a to the discharge chamber 32 are performed intermittently, so pressure fluctuations (pulsation) of the fluid occur in the suction chamber 21 and the discharge chamber 32. Due to this, sometimes vibration or a groaning-like noise occurs, so to suppress pressure fluctuations in the suction chamber 31 and discharge chamber 32 and smooth the flow of fluid into the compressor and the flow of fluid out of it, the conventional compressor has been designed to make the capacity of the suction chamber or discharge chamber as large as possible. Therefore, by common sense, enlargement of the drive plate type compressor as a whole by the amount of increase of capacity of the suction chamber and discharge chamber as a measure for preventing vibration and noise is an unavoidable problem.
Still another example of a conventional compressor is described in Japanese Unexamined Patent Publication (Kokai) No. 2000-18172. The structure of this compressor as a whole is shown in FIG. 44, which part of it, that is, the part of the capacity control valve, is shown in FIG. 45. This compressor falls under the category of a drive plate type variable capacity compressor. The housing forming the shell is comprised of three partsxe2x80x94a front housing 1, a cylinder block 2, and a rear housing 3xe2x80x94joined by through bolts 40. Pistons 7 are inserted into a plurality of cylinder bores 21 formed in the center cylinder block 2 and are forced to engage in reciprocating motion by a common drive plate 5 through shoes 8. The drive plate 8 is driven to rotate by a long shaft passing through its center and extending to the center of the cylinder block 2. The front end of the shaft 4 is axially supported by a bearing 64 provided in the cylinder block 2.
In the operating state, due to the rocking motion of the drive plate 5 rotating together with the shaft 4, the plurality of pistons 7 engage in reciprocating motion in their cylinder bores 21 to expand and compress working chambers 21a and thereby cause a fluid such as a refrigerant to pass through a suction valve and be sucked into the working chambers formed at the top faces of the pistons in the cylinder bores 21 from a suction chamber 31 formed at the outer periphery of the rear housing 3 so as to be compressed, then pass through a discharge valve and be discharged into a discharge chamber 32 formed at the center of the rear housing 3. This compressor enables the tilt angle of the drive plate 5 to be smoothly changed, so enables the discharge capacity to be continuously changed.
In a compressor as shown in FIG. 44, it is possible to change the tilt angle of the drive plate 5 so as to simultaneously change the strokes of all of the pistons 7 and control the discharge capacity of the compressor as a whole to smoothly change. This control involves operating a capacity control valve 33 attached to the rear housing 3 to change the back pressure of all of the pistons 7, that is, the pressure in a drive plate chamber 1a formed in the front housing 1. Since the capacity control valve 33 is provided so as to stick out in the axial direction from the rear housing 3, the conventional compressor had the problem that the provision of the capacity control valve 33 remarkably increased the length of the compressor in the axial direction.
There are reasons why the capacity control valve 33 was generally placed at that position in a conventional compressor despite the existence of such a problem. The first reason is that even if trying to provide the capacity control valve 33 inside the compressor, there is just not enough space for holding the capacity control valve 33 inside the compressor. The second reason is that the capacity control valve 33 receives both of a low pressure fluid in the suction chamber 31 and a high pressure fluid in the discharge chamber 32 to create a pressure of any level between the high pressure and low pressure and supplies the same to the drive plate chamber 1a, so if attaching the capacity control valve 33 to the rear housing 3 formed with the suction chamber 31 and the discharge chamber 32, the flow path connecting them becomes shorter and simpler in configuration. The third reason is that if the capacity control valve 33 is provided at the outer periphery of the cylinder block 2 rather than the rear housing 3, the housing of the compressor would stick out largely in the radial direction, the position of provision of the capacity control valve 33 and the compressor as a whole would become bulkier, and further the routing of the flow path would become more difficult.
Note that in the prior art shown in FIG. 44 and FIG. 45, a tube 36 is provided for guiding the motion of a plunger 35 inside a solenoid coil 34 of the capacity control valve 33. This tube 36 is not just a guide, but also a seal tube for preventing the high pressure fluid etc. in the discharge chamber 32 from passing through the inside of the capacity control valve 33 and leaking out to the atmosphere, so both a high air-tightness and pressure resistance are required as performance. Further, this tube 36 has to be one which allows magnetic flux to permeate efficiently for making the plunger 35 operate efficiently by the solenoid coil 34. It is however extremely difficult to meet all of these conditions. Therefore, for example, the problem arises that if stressing the sealability and thereby sacrificing the magnetic permeability, the magnetic efficiency falls or else the structure becomes complicated.
The present invention was made in consideration of the above-mentioned problems in the prior art and has as its object to provide a compressor of a novel configuration enabling these problems to be solved.
The present invention further has as its object to deal with the vital problems of a drive plate type compressor and provide a much smaller drive plate type compressor than a conventional compressor having the same degree of discharge capacity by making the capacities of the suction chamber and discharge chamber as large as possible to thereby sufficiently suppress pressure fluctuations in the fluid and introducing a new means not increasing the size of the compressor as a whole while preventing vibration and noise.
The present invention further has as its object to provide a much smaller drive plate type compressor than a conventional compressor having the same degree of discharge capacity by introducing a new means not requiring an increase of the size of the compressor as a whole when providing a capacity control valve in a compressor such as a drive plate type variable capacity compressor.
The present invention, as a first means for solving the above problems, provides a compressor comprising a shaft axially supported by only a front end of a housing through a bearing and receiving rotational power from a power source; a drive plate rotating by being connected with and supported by the shaft and able to tilt with respect to the shaft; a shoe holding plate supported by the drive plate through a holding plate thrust bearing forming a roller bearing and thereby taking the same tilt angle, but prevented from rotating; a plurality of shoes able to engage with a plurality of shoe guide grooves formed in a radial direction at a peripheral part of the shoe holding plate and slide in the radial direction; a drive thrust bearing arranged between the shoes and the drive plate; a plurality of pistons directly connected with the shoes and engaging in reciprocating motion, inserted in cylinder bores to suck in and compress a fluid, and preventing rotation of the shoe holding plate; and means for changing the tilt angle of the drive plate and the shoe holding plate to change a discharge capacity.
In this compressor, the shoes connected to the pistons support the load required for the compression operation through the drive thrust bearing arranged between the shoes and the drive plate, so there is no sliding and frictional sliding at a high speed while supporting the load as in the shoes of a conventional drive plate type compressor and therefore there is no longer any liability of seizing due to friction of sliding parts, increased mechanical loss, etc.
Further, the shoes are biased to the drive thrust bearing side by the shoe holding plate formed with the plurality of shoe guide grooves in the radial direction to prevent occurrence of clearance between the drive plate and drive thrust bearing and the shoes. This shoe holding plate is rotatably supported relatively on the axis of rotation of the drive plate, so even when changing the tilt angle of the drive plate to change the discharge capacity of the compressor, it completely follows the tilt of the drive plate to take the same tilt angle. Therefore, the clearance between the shoes and drive plate is constantly held the same and there is no trouble of the clearance between the two increasing when changing the discharge capacity.
In the compressor of the present invention, each shoe may be comprised of a shoe body provided with a spherical depression engaging with a spherical end provided at a piston and a shoe flange sticking out to the sides integrally from the shoe body. In this case, since the shoe engaged with the piston engages with a shoe guide groove formed in the radial direction in the shoe holding plate by the shoe body and the shoe flange provided there, the shoe is reliably biased to the drive plate side. Note that the area of the contact part between a shoe and the shoe holding plate desirably is made larger from the viewpoint of reducing the planar load.
In the past, this type of shoe was generally mostly disk shaped, but if the diameter of the shoe is increased to increase the contact area as explained above, the shoe sticks out from the periphery of the drive plate. Therefore, the drive plate becomes larger in diameter. As a result, the girth of the compressor becomes larger and, at the center side, the problem arises of the shoe interfering with the center of the shoe holding plate. As opposed to this, in the case of the compressor of the present invention, since the shoe can be made a substantially rectangular shape, it is smaller than a disk shaped shoe and there is no liability of it sticking out from the periphery of the drive plate or interfering at the center. Despite this, it can reliably engage with the shoe holding plate and increase the contact area with the shoe holding plate.
The present invention further provides a compressor comprised of a shaft receiving rotational force from a power source; a drive plate rotating by being connected with and supported by the shaft and able to tilt with respect to the shaft; a shoe holding plate supported by the drive plate through a holding plate thrust bearing forming a roller bearing and thereby taking the same tilt angle; a plurality of pistons inserted in cylinder bores to suck in and compress a fluid and preventing rotation of the shoe holding plate; and a mechanism for converting tilted rotary motion of the drive plate to reciprocating motion of the pistons, wherein, as a means for changing the tilt angle of the drive plate to change a discharge capacity, a slide link mechanism comprised of a plurality of pins and a plurality of guide grooves with which the pins engage is provided at a position away from the axial center of the shaft for connecting the shaft and the drive plate.
In this compressor, the drive plate and shoe holding plate can of course smoothly change in tilt angle with respect to an imaginary plane perpendicular to the shaft while maintaining suitable postures and positions. Due to this mechanism, there is no longer a need for the shaft to pass through the drive plate and the center of a member like the shoe holding plate included in the mechanism for converting the tilted rotary motion of the drive plate to reciprocating motion of the pistons, so it is possible to reduce the size of the bearing means such as the holding plate thrust bearing naturally becoming necessary to rotatably connect the member like the shoe holding plate to the drive plate. Therefore, it is possible to reduce the size of the compressor as a whole.
In the compressor of the present invention, the shaft may be axially supported by only a front end of the compressor housing. In this case, there is no need at all for the shaft to pass through the drive plate, shoe holding plate, or other such members, so the compressor can be made smaller as a whole.
In the compressor of the present invention, it is possible to configure each piston from a conical shoulder part formed integrally with a spherical end in advance, a cylindrical part joined with the conical shoulder part, and a bottom part joined with the cylindrical part; configure it from a conical shoulder part formed integrally with a spherical end in advance, a cylindrical part formed integrally with the conical shoulder part in advance, and a bottom part joined with the cylindrical part; configure it from a conical shoulder part formed integrally with a spherical end in advance, a cylindrical part joined with the conical shoulder part, and a bottom part formed integrally with the cylindrical part in advance; configure it from a conical shoulder part joined with a spherical end, a cylindrical part joined with the conical shoulder part, and a bottom part joined with the cylindrical part; and configure it from a conical shoulder part joined with a spherical end, a cylindrical part formed integrally with the conical shoulder part in advance, and a bottom part formed integrally with the cylindrical part in advance. Due to this, a tough piston with no parts of stress concentration is obtained.
In the compressor of the present invention, the parts forming each piston may be strongly joined by welding or calking. Further, the piston may be made a hollow structure. Due to this, the piston is lightened, so the amount of power required for driving the piston becomes comparatively smaller than when preventing unreasonable force from acting on the mechanism supporting or driving the piston.
The piston may be fabricated from a ferrous material. Due to this, the strength and durability are greatly improved over the aluminum piston frequently used in the past. If made a hollow structure, the increase in weight also does not become a problem.
Further, it is possible to provide a torsion coil spring biasing the drive plate in a direction reducing the tilt angle in a state where the tilt angle of at least the drive plate is large and in a direction increasing the tilt angle in an operating state where the tilt angle is zero or minimal. By providing this torsion coil spring, when the tilt angle of the drive plate is zero or minimal, the torsion coil spring biases the drive plate to increase its tilt angle, so if there is no force acting against this, the tilt angle of the drive plate will increase and therefore quick response will be possible when the need next arises to increase the discharge capacity.
The torsion coil spring may be made a single continuous spring. Due to this, the biasing means for increasing the tilt angle of the drive plate becomes simpler in configuration and the number of parts is reduced compared with the case of using two coil springs as in the past.
In the compressor of the present invention, each shoe may be comprised of a shoe body and a shoe flange, and the shoe body may be formed by casting so as to surround a spherical end at the piston side. Further, the piston may be formed by casting so as to surround a spherical end of a connecting rod side where the piston is connected with a shoe. Therefore, in both cases, since the shape of the spherical end is transferred to the shoe surrounding it or the spherical depression of the piston side by casting, there is no need for mechanically processing the spherical depression and an equivalent surface precision can be automatically obtained. Further, since there is no calking performed, the thickness of the member forming the depression can be increased and strengthened at will.
In the compressor of the present invention, as the drive thrust bearing, one comprised of a large number of short rollers arranged radially divided into groups on a plurality of concentric circles can be used. In this case, since the rollers are short, the difference in peripheral speeds at the two ends becomes smaller and the slip ratio is reduced. Since a large number of rollers are arranged on concentric circles to bear the load, it is possible to support a large load equivalent to the case of using long rollers with a large slip ratio. Therefore, the wear of the drive thrust bearing is reduced and the power loss also falls.
More specifically, a large number of short rollers arranged radially divided into groups on a plurality of concentric circles may be held by a separate holder for each group of rollers on each concentric circle. Further, a large number of short rollers arranged radially divided into groups on a plurality of concentric circles may be held by a common holder. Further, a plurality of rollers arranged in a radial direction on the same line among a large number of short rollers arranged radially divided into groups on a plurality of concentric circles may be held by a same window opening formed in a common holder.
In the compressor of the present invention, as the shoe held by the shoe holding plate, one provided with a shoe flange integral with a shoe body may be used. The planar shape of the shoe flange may be made a substantially rectangular shape. Alternatively, the planar shape of the shoe flange may be made a substantially fan shape. Further alternatively, the planar shape of the shoe flange may be made substantially a shape intermediate between a rectangular shape and fan shape. In any case, compared with the case of a planar large circular shape of the shoe flange, the flange can be made as large as possible while avoiding mutual interference, so the sliding action of the shoes becomes smoother and therefore the discharge capacity can be changed smoothly.
In the compressor of the present invention, it is possible to remove the shoe holding plate and drive thrust bearing and have the shoes directly slidingly engage with the drive plate. In this case, the engaging parts of the drive plate and shoes are configured as often used in the past, but the shaft does not pass through the drive plate, and the drive plate is supported by only the front end of the housing. Therefore, even with this configuration, the effects of the present invention explained above can be obtained.
The present invention, as another means for solving the above problems, provides a compressor comprising a shaft receiving rotational power from a power source; a plurality of pistons engaging in reciprocating motion by being driven connected to the shaft; a cylinder block formed with a plurality of cylinder bores receiving the pistons; a suction chamber from which the pistons cause fluid to be sucked into working chambers formed in the cylinder bores; a discharge chamber to which fluid compressed in the working chambers is discharged; at least one muffler chamber forming an open space formed using a dead space of the cylinder block; and a communication port for communicating the muffler chamber and at least one of the suction chamber and discharge chamber.
In this compressor, since provision is made of a communication port for communicating at least one muffler chamber forming an open space formed using the dead space of the cylinder block with at least one of the suction chamber and discharge chamber, the suction chamber or discharge chamber communicated with the muffler chamber becomes substantially the same in state as if increased in capacity. As a result, suction or discharge pulsation is suppressed by the large capacity of the suction chamber or discharge chamber. Since however the muffler chamber is formed using the dead space of the cylinder block, the size of the compressor does not become larger due to the provision of the muffler chamber. By providing the drive plate at the shaft, it is possible to form a drive plate type compressor making the pistons engage in reciprocating motion through the drive plate. Similar effects are obtained in this case as well.
When the drive plate is connected to the shaft so as to be able to be changed in tilt angle, the compressor operates as a drive plate type variable capacity compressor. Therefore, not only are similar effects to the above case obtained, but also the discharge capacity can be smoothly changed. Further, it is possible to support the shoe holding plate taking the same tilt angle as the drive plate, but prevented from rotation, by the drive plate through the drive thrust bearing and possible to guide the plurality of shoes engaged with the ends of the pistons so as to be able to freely slide in the radial direction by the plurality of shoe guide grooves formed in the radial direction at the periphery of the shoe holding plate. Due to this, the shoes do not directly frictionally engage with the drive plate, so an efficient compressor is obtained. Further, if configuring each shoe by a shoe body provided with a spherical depression engaging with the spherical end provided at a piston and a pair of shoe flanges sticking out to the two sides integrally from the shoe body and engaging with the shoe holding plate, the shoe is smoothly guided by the shoe holding plate. In both cases, similar effects to the above case are obtained.
In this compressor, as the means for changing the tilt angle of the drive plate to change a discharge capacity and for connecting the shaft and the drive plate, it is possible to provide a slide link mechanism comprised of a plurality of pins and a plurality of guide grooves with which the pins engage at a position away from the axial center of the shaft. In this case as well, it is possible to axially support the shaft by just the front end of the housing. In both cases, the shaft does not pass through the drive plate and extend to the cylinder block, so a dead space occurs at the cylinder block. Therefore, it is possible to form a muffler chamber of a large capacity using this dead space, so it becomes possible to effectively reduce the suction or discharge pulsation.
The present invention, as still another means for solving the above problems, provides a compressor comprising a plurality of pistons for compressing a fluid; a cylinder block formed with a plurality of cylinder bores for receiving the pistons; and a capacity control valve for changing a discharge capacity of the compressor attached using a dead space of the cylinder block where the cylinder bores are not formed.
In this compressor, since a capacity control valve for changing the discharge capacity of the compressor is provided using some sort of dead space formed in the cylinder block, the size of the compressor will not become larger due to the provision of the capacity control valve. Since the capacity control valve is provided inside the compressor, if designing the capacity control valve to be immersed in the fluid to be compressed, the only part which need be made hermetic against the outside in the capacity control valve is the place where the signal line is led out. Therefore, sealing the capacity control valve becomes easier than in a conventional compressor.
Specifically, this compressor can be embodied comprising a shaft receiving rotational force from a power source; a drive plate rotating by being driven connected with the shaft and able to tilt with respect to the shaft; a plurality of pistons engaging in reciprocating motion by engaging with the drive plate; a cylinder block formed with a plurality of cylinder bores receiving the pistons in parallel with the shaft around a center axis of the shaft; and a capacity control valve attached using a dead space at a center of the cylinder block and able to change a tilt angle of the drive plate so as to change a discharge capacity of the compressor.
The present invention, as another means to solve the above problems, provides a drive plate type variable capacity compressor provided with a drive plate driven to rotate by being connected to a shaft, making a plurality of pistons engage in reciprocating motion through this drive plate, and able to smoothly change the discharge capacity by changing the tilt angle of the drive plate, wherein the plurality of cylinder bores receiving the plurality of pistons are formed parallel to the shaft in the cylinder block around the center axis of the shaft and wherein a capacity control valve for changing the tilt angle of the drive plate is provided using the dead space formed at the center of the cylinder block. In this case as well, effects similar to those of the above case are obtained.
It is possible to change the pressure in the drive plate chamber housing the drive plate by the above capacity control valve so as to change the discharge capacity of the compressor. The pressure of the drive plate chamber is the back pressure of all of the pistons, so if the pressure in the drive plate chamber is changed by the operation of the capacity control valve, the state of balance with the reaction force of the fluid compressed by the pistons in the working chambers in the cylinder bores will change, the average axial direction position of the pistons will change, and the tilt angle of the drive plate will change to change the strokes of the pistons, so the discharge capacity of the compressor will change smoothly.
Further, in this compressor, it is possible to support a shoe holding plate taking the same tilt angle as the drive plate, but prevented from rotating, by the drive plate through a drive thrust bearing and to guide the plurality of shoes engaging with ends of pistons so as to be able to slide freely in the radial direction by a plurality of shoe guide grooves formed in the radial direction at a peripheral part of the shoe holding plate. Due to this, the shoes do not directly engage frictionally with the drive plate, so an efficient drive plate type variable capacity compressor is obtained. In this case as well, similar effects to the above are obtained.
Further, in this compressor, as a means for changing the tilt angle of the drive plate to change a discharge capacity and for connecting the shaft and the drive plate, a slide link mechanism comprised of a plurality of pins and a plurality of guide grooves with which the pins engage may be provided at a position away from the axial center of the shaft. Further, the shaft may be axially supported by just a front end of the housing through a bearing. In both cases, since the shaft does not pass through the drive plate and extend to the cylinder block, a large dead space occurs in the cylinder block. Therefore, a capacity control valve can be provided using the dead space in the cylinder block, so the size of the compressor will not become greater.
Further, in this compressor, the capacity control valve can create any pressure between the pressure of the suction chamber and the pressure of the discharge chamber. Due to this, the discharge capacity of the compressor can be smoothly changed.